In recent years, chargeable/dischargeable lithium ion secondary batteries (hereinafter, simply referred to as batteries) have been used as drive power sources of hybrid vehicles and portable electronic devices such as a notebook-sized personal computer and a video camcorder.
As for such batteries, for example, Patent Document 1 discloses a lithium ion secondary battery in which two kinds of carbonaceous materials (negative active material particles), i.e., graphite and low-temperature carbonized carbon (low crystalline carbonaceous materials), are used for a negative electrode material (a negative active material layer) of a negative electrode (a negative electrode sheet)